Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Collagen Type VI”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources
PubMed1992

Isolation, characterization, and localization of cardiac collagen type VI. Associations with other extracellular matrix components.

We have isolated and characterized collagen type VI from murine, canine, and nonhuman primate hearts. In the three species studied, collagen type I was the major collagenous component of the cardiac interstitium (80% of total collagen), whereas collagen type VI represented approximately 5% of total collagen. To define the exact distribution of collagen type VI and its possible interactions with other components of the cardiac extracellular matrix, collagen types I, III, IV, and VI, laminin, and fibronectin were localized in the rat myocardium by immunohistochemistry, using monospecific antibodies. In the rat myocardium, collagen type VI was prevalent in the media and adventitia of muscular arteries, in fine connective tissue septa, in the area surrounding capillaries, and in the delicate endomysium in proximity to myocardial cells. When compared with the immunohistochemical localization of collagen types I, III, and IV, laminin, and fibronectin, the continuity and hierarchical organization of the cardiac extracellular matrix became apparent. The matrix forms a continuous network extending from the pericardium to the endocardium. Furthermore, there is an arborescent hierarchy in the system such that collagen type I is more prevalent in the wider septa, collagen type III being more obvious in medium-sized branches, and fibronectin and collagen type VI prevailing in the terminal (pericellular) aspects of the network. In this pericellular location, fibronectin and collagen type VI, by means of specific interactions, may act as anchor components linking the myocardial cell basement membranes not only to the extracellular matrix but also to the cardiac interstitial cells. This continuity, organization, and coupling of the cardiac extracellular matrix appears well suited to integrate and distribute the physical stress generated by the continuous contraction and relaxation of the myocardium.

Animals↗
PubMed1991

Interaction of intact type VI collagen with hyaluronan.

The capacity of non-pepsinyzed type VI collagen to bind to hyaluronan was investigated. Type VI collagen was extracted from bovine meniscal cartilage with 6 M GuHCl and purified by extraction of PEG precipitates and dissociative Sephacryl S-500 HR chromatography. Type VI collagen, detected with a monoclonal antibody, bound in 0.5 M NaCl to hyaluronan-coated micro-wells, the degree of binding being higher at 37 degrees C than 23 degrees C and 4 degrees C. Incubation of type VI collagen in competitive inhibition assays with testicular hyaluronidase digests of hyaluronan in liquid phase, reduced binding of the protein to hyaluronan-coated microwells to background levels. Thus, non-pepsinyzed type VI collagen binds to hyaluronan in vitro.

Animals↗
PubMed1995

The macromolecular structure of type-VI collagen. Formation and stability of filaments.

Type-VI collagen microfilaments were directly isolated from human amnion without using strong denaturing reagents. The microfilaments were characterized by electron microscopy, SDS/PAGE and immunoprecipitation. There was no evidence of other components bound to the isolated filaments and no covalent bonds between adjacent tetramers. The association between tetramers was further analyzed by studying the affinity between globular domains and the helix of type-VI collagen. Solid-phase-binding assays and conventional column chromatography showed that the globular domains have a high affinity for each other and for the helices of type-VI collagen, indicating that filaments may be assembled and stabilized in the absence of additional components. Hyaluronan did not stabilize the filaments nor facilitate the assembly of tetramers into filaments. The interaction between domains was also studied after modifying the sugar moieties of type-VI collagen globular domains and monomeric triple-helical domains. The oligosaccharides are involved in helix-helix interactions but not in interactions of the globular domains with each other or with the triple helix.

Actin Cytoskeleton↗
PubMed1999

The distribution of type VI collagen in the developing tissues of the bovine femoral head.

Type VI collagen appears central to the maintenance of tissue integrity. In adult articular cartilage, type VI collagen is preferentially localised in the chondron where it may be involved in cell attachment. In actively remodelling developing cartilage, the distribution is less certain. We have used confocal immunohistochemistry and in situ hybridisation to investigate type VI collagen distribution in third trimester bovine proximal femoral epiphyses. In general, type VI collagen immunofluorescence was concentrated in the chondrocyte pericellular matrix, with staining intensity strongest in regions which persist to maturity and weakest in regions that remodel during development. Type VI collagen was also present in cartilage canals. In the growth plate and around the secondary centre of ossification, the intensity of type VI collagen stain rapidly decreased with chondrocyte maturation and was absent at hypertrophy, except where canal branches penetrated the growth plate and stain was retained around the adjacent chondrocytes. In situ hybridisation confirmed the presence of type VI collagen mRNA in cartilage canal mesenchymal cells but the signal was low in chondrocytes, suggesting minimal levels of synthesis and turnover. The results are consistent with a role for type VI collagen in stabilising the extracellular matrix during development.

Animals↗
PubMed1988

Ultrastructure of type VI collagen in human skin and cartilage suggests an anchoring function for this filamentous network.

An mAb was used in conjunction with immunoelectron microscopy to study the ultrastructure and distribution of the type VI collagen network. Type VI collagen in femoral head and costal cartilage was found distributed throughout the matrix but concentrated in areas surrounding chondrocytes. Three-dimensional information gained from high voltage stereo pair electron microscopy showed that the type VI collagen network in skin was organized into a highly branched, open, filamentous network that encircled interstitial collagen fibers, but did not appear to interact directly with them. Type VI collagen was also found concentrated near basement membranes of nerves, blood vessels, and fat cells although in a less organized state. Labeling was conspicuously reduced close to the epithelial basement membrane in the region of the anchoring fibrils. No labeling of basement membranes was seen. Based on these observations it is suggested that the type VI collagen forms a flexible network that anchors large interstitial structures such as nerves, blood vessels, and collagen fibers into surrounding connective tissues.

Age Factors↗
PubMed1995

Biosynthesis of type VI collagen by glioblastoma cells and possible function in cell invasion of three-dimensional matrices.

The biosynthesis of type VI collagen was studied in human glioblastoma cell line, U-87 MG. The effects of ascorbic acid on type VI collagen synthesis and secretion were investigated. After ascorbic acid treatment, type VI collagen in cell layers increased from 4.48% in control to 6.63% in the ascorbic acid treated cultures, an increase of 48%. The effect of ascorbic acid on type VI collagen synthesized by glioblastoma cells was lower than that reported for osteosarcoma cells (Engvall et al., 1986). The reason for these differences is still under investigation. The function of type VI collagen in glioblastoma cells is still unknown. We utilized the collagen gel system to elucidate the possible roles of type VI collagen in glioblastoma cells in vitro. Glioblastoma cells in collagen gels showed a stellate shape with long, branched processes in all directions. The strong positive reactivity of type VI collagen detected on cell bodies and cell processes by anti-type VI collagen antibody indicated that this specific collagen was associated with cell surfaces and processes, without releasing or diffusing into the gels. Type VI collagen was directly involved in the cell process extension. When living cells were treated with anti-type VI collagen antibody, a variation of cell morphology was observed. Instead of a stellate shape with processes, cells formed clusters without or with very short processes. These data suggest that type VI collagen, synthesized and secreted by glioblastoma cells, may play a role in tumor cell adhesion and spreading, and enhance cell process extension, penetration, and invasion into collagen gels.

Antibodies↗
PubMed1995

Platelet adhesion and aggregation on human type VI collagen surfaces under physiological flow conditions.

Type VI collagen is a subendothelial constituent that binds von Willebrand factor (vWF) and platelets. The interaction of platelets with type VI collagen and the roles of platelet glycoprotein (GP) receptors and vWF were studied under flow conditions using epi-fluorescent videomicroscopy coupled with digital image processing. We found that surface coverage was less than 6% on collagen VI at a relatively high-wall shear rate (1,000 s-1) and was approximately 60% at a low-wall shear rate (100 s-1). The molecular mechanisms involved in low-shear platelet binding were studied using monoclonal antibodies to platelet GPIb and GPIIb-IIIa, and polymeric aurin tricarboxylic acid. Anti-GPIIb-IIIa was the most effective in eliminating adhesion (surface coverage, 0.8%), followed by anti-GPIb (4.3%), and ATA (12.6%). Experiments with von Willebrand disease blood indicate that vWF is involved in platelet adhesion to collagen VI at 100 s-1. In the absence of vWF, there may be direct binding of platelet GPIIb-IIIa complexes to collagen VI. Adhesion and aggregation on collagen VI are different in shear rate dependence from collagen I. Our results suggest a possible role for collagen VI and vWF in platelet adhesion and aggregation in vascular regions with low shear rates.

Animals↗
PubMed1987

Type VI collagen of the intervertebral disc. Biochemical and electron-microscopic characterization of the native protein.

The collagen framework of the intervertebral disc contains two major fibril-forming collagens, types I and II. Smaller amounts of other types of collagen are also present. On examination of the nature and distribution of these minor collagens within bovine disc tissue, type VI collagen was found to be unusually abundant. It accounted for about 20% of the total collagen in calf nucleus pulposus, and about 5% in the annulus fibrosus. It was discovered by serially digesting disc tissue with chondroitin ABC lyase and Streptomyces hyaluronidase that native covalent polymers of type VI collagen could be extracted. Electron micrographs of this material prepared by rotary shadowing revealed the characteristic dimensions of tetramers and double tetramers of type VI molecules, with their central rods and terminal globular domains. Molecular-sieve column chromatography on agarose under non-reducing non-denaturing conditions gave a series of protein peaks with molecular sizes equivalent to the tetramer, double tetramer and higher multimers. On SDS/polyacrylamide-gel electrophoresis after disulphide cleavage, these fractions of type VI collagen all showed a main band at Mr 140,000 and four lesser bands between Mr 180,000 and 240,000. On electrophoresis without disulphide cleavage in agarose/2.4% polyacrylamide only dimeric (six chains) and tetrameric (12 chains) forms of type VI molecules were present. The ability to extract all the type VI collagen of the tissue in 4 M-guanidinium chloride, and absence of aldehyde-mediated cross-linking residues on direct analysis, showed that, in contrast with most matrix collagens, type VI collagen does not function as a covalently cross-linked structural polymer.

Animals↗
PubMed2000

Type VI collagen expression during growth of human ovarian follicles.

OBJECTIVE: To identify type VI collagen expression in human ovarian follicles during follicular growth. DESIGN: In vitro experiment. SETTING: Department of Obstetrics and Gynecology, Wakayama Medical College, Japan. PATIENT(S): Regularly cycling women who underwent adnexectomy. INTERVENTION(S): Immunohistochemistry and in situ hybridization for human type VI collagen. MAIN OUTCOME MEASURE(S): Expression of type VI collagen. RESULT(S): Expression of type VI collagen was observed in the theca cell layers during folliculogenesis, whereas no expression of type VI collagen was observed in the granulosa cell layers at the mRNA and protein levels. As the follicles grew, immunostaining for type VI collagen became intense in the theca cell layers, especially the theca externa. In preovulatory follicles, however, weak, fragmented, or discontinuous immunostaining of the theca cell layers was observed. This fragmented or discontinuous immunostaining was evident predominantly in the apical area of preovulatory follicles rather than in the basal area. CONCLUSION(S): Type VI collagen is present in the theca cell layers of follicles during folliculogenesis and plays an important role in interactions between the theca cells and extracellular matrix. These interactions may lead to changes in the shape, proliferation, migration, or differentiation of follicular cells during follicular development, maturation, and ovulation.

Adult↗
PubMed1996

Altered type VI collagen synthesis by keratoconus keratocytes in vitro.

Type VI collagen and gelatinase A are synthesized by human keratocytes in vitro. Keratoconus is a corneal disease that has increased gelatinase A activity. Normal keratocyte culture media analyzed by Western blotting with polyclonal antibody to type VI collagen showed a single 140 kDa band that increased in intensity after phorbol ester treatment. The same 140 kDa band was absent in media collected from keratoconus keratocytes cultured with or without phorbol ester. We speculate that in keratoconus keratocyte cultures, type VI collagen may be degraded or modified by the increased gelatinase A activity so as not to be recognized by the type VI antibody.

Blotting, Western↗
PubMed2006

Identification, content, and distribution of type VI collagen in bovine tendons.

Tendon composition changes according to differentiation, mechanical load, and aging. In this study, we attempted to identify, localize, and quantify type VI collagen in bovine tendons. Type VI collagen was identified by the electrophoretic behavior of the alpha chains and Western blotting, and by rotary shadowing. Type VI collagen was extracted from powdered tendon with three sequential 24-h extractions with 4 M guanidine-HCl. The amount of type VI collagen was determined by enzyme-linked immunosorbent assay for purely tensional areas and for the compressive fibrocartilage regions of the deep flexor tendon of the digits, for the corresponding fetal and calf tendons, and for the extensor digital tendon. The distal fibrocartilaginous region of the adult tendon was richer in type VI collagen than the tensional area, reaching as much as 3.3 mg/g (0.33%) of the wet weight. Calf tendons showed an accumulation of type VI at the fibrocartilage site. Immunocytochemistry demonstrated that type VI collagen was evenly distributed in the tensional areas of tendons but was highly concentrated around the fibrochondrocytes in the fibrocartilages. The results demonstrate that tendons are variable with regard to the presence and distribution of type VI collagen. The early accumulation of type VI collagen in the region of calf tendon that will become fibrocartilage in the adult suggests that it is a good marker of fibrocartilage differentiation. Furthermore, the distribution of type VI collagen in tendon fibrocartilage indicates that it organizes the pericellular environment and may represent a survival factor for these cells.

Animals↗
PubMed1994

Experimental in vivo and in vitro formation of type VI collagen periodic fibrils in chorionic villi of human placenta.

The distribution of type VI collagen in the chorionic villi of normal human term placenta was studied. Since 100 nm periodic fibrils (type VI collagen periodic fibrils) are known to form in the tendon, cornea and cultured fibroblasts by incubation with acidic ATP solution, we incubated the placental tissue with 20 mM ATP, fixed it with Karnovsky's fixative and examined under an electron microscope. Type VI collagen periodic fibrils widely occurred in the interstitial connective tissue, especially close to the basal lamina. By cryo-immunoelectron microscopy, labeling for collagen type VI was found in the area between the trophoblastic basal lamina and the endothelial basal lamina. Furthermore, we extracted type VI collagen from the human placenta and brought both extract and residues into ATP treatment. Periodic structure formation was rare in extracted preparation compared with residues. The results served to clarify the mechanism of fibril formation in the tissue.

Adenosine Triphosphate↗
PubMed1986

Avian type VI collagen. Monoclonal antibody production and immunohistochemical identification as a major connective tissue component of cornea and skeletal muscle.

Two monoclonal antibodies have been characterized as being against avian type VI collagen. By competition ELISA, the antibodies bound to the native type VI collagen molecule but not to its separated chains or to any of the other native collagen types tested. By rotary shadowing analysis of complexes of antibody-type VI collagen monomers, one of the antibodies (VI-EC6) has been shown to bind to a site in the triple helical domain of the molecule. The site at which this antibody binds to the dimeric form of type VI collagen is consistent with the previously proposed model for a supramolecular organization of the molecule (Furthmayr et al., Biochem j 211 (1983) 303) in which the monomers are arranged in an antiparallel, slightly staggered overlap. Immunofluorescence analyses of sections of chicken eyes and skeletal muscle demonstrate that type VI collagen is a major component of most stromal matrices.

Animals↗
PubMed1987

The tissue form of chicken type VI collagen.

We have purified intact type VI collagen from chicken gizzard. The protein was found to consist of a 130 kDa, a 140 kDa and a 180-200 kDa subunit. The 130 kDa and 140 kDa subunits were obtained in equimolar amounts and identified as the alpha 2 (VI) and the alpha 1 (VI) chains, respectively. The third subunit was usually obtained in the form of 3-4 closely related polypeptides, which may represent different processing or modification products of the alpha 3 (VI) chain.

Animals↗
PubMed1989

Distribution of type VI collagen in the bovine cornea.

Using a specific polyclonal antibody against type VI collagen, the distribution of type VI collagen in the bovine cornea was investigated by indirect immunofluorescence microscopy and immunoelectron microscopy. By immunofluorescence, type VI collagen was detectable throughout the stroma. In addition to the uniform but relatively weak signals, a laminar pattern similar to the arrangement of stromal lamellae was clearly seen. Consistent with the immunofluorescent pattern, immunoelectron micrographs showed strong linear reactions located in the interlamellar spaces. The reactions were also observed in the pericellular region of the keratocytes. Epithelium, Descemet's membrane and endothelium were negative.

Animals↗
PubMed1996

Spatial and temporal changes of type VI collagen expression during mouse development.

The expression of type VI collagen has been studied in mouse tissues. By Northern blotting, the mRNA for the alpha 1 (VI) chain was detectable in whole embryos at 10.5 days postcoitum and steeply increased afterward. The messenger levels were high at birth, but decreased rapidly in the following days, reaching low levels in adult animals. In 2-month-old mice, lung, skin, adrenal gland, heart, skeletal muscle and tail and fat were among the most active producers of alpha 1 (VI) mRNA. In situ hybridization first identified mRNA for alpha 1 (VI) collagen in mesenchymal cells of 10.5-day embryos in various locations, including serosae, branchial arches, large blood vessels and the cephalic mesenchyme. Staining increased at later stages of development and most connective tissues were positive at 16.5 days and later. Strongly staining tissues were joints, intervertebral disks, perichondrium, periostium, dermis, skeletal muscle and heart valves, whereas cartilage and bone were very poorly labelled. Epithelia and the central nervous system were completely negative. In several organs, notably lung, salivary glands and the digestive tract, staining was concentrated underneath epithelia. This staining pattern was different from that for collagen type I, which was evenly distributed in the subepithelial mesenchyme. The pattern of distribution of the protein, revealed by immunocytochemistry, was coincident with that of the alpha 1 (VI) mRNA. In addition, the results confirmed that type VI collagen is preferentially deposited in the pericellular environment. This was particularly evident in skeletal muscle. The data show that type VI collagen is mainly produced by mesenchymal cells and suggest a role for the protein in delineating the boundary of distinct domains in connective tissue.

Animals↗
PubMed1990

Increased expression of type VI collagen genes in systemic sclerosis.

The expression of type VI collagen genes in affected skin from patients with systemic sclerosis (SSc) was examined by in situ hybridizations with a human alpha 2(VI) collagen sequence-specific complementary DNA. Five patients with diffuse, rapidly progressive SSc of recent onset (less than 12 months) were studied. The results showed increased expression of alpha 2(VI) collagen messenger RNA transcripts in the skin of scleroderma patients compared with that in the skin of normal subjects. These findings indicate that alterations in the expression of type VI collagen genes, similar to those previously described for types I and III collagen, are present in the affected skin of SSc patients. These alterations may result in excessive tissue accumulation of type VI collagen and may play a role in the progressive skin induration and sclerosis that are prominent features of SSc.

Adult↗